I don't even build speakers.
I'm more of a consumer when it comes to these things. I like to read about Xmax and all this other stuff.
but when it comes down to it,
I just like to mix on a system that fits the room.
I thought of one solution for you.. if you have any crappy speakers already there.. just leave them there and plug a dummy cable into the back of them.. then just get one 718 for the room and place it closest to the center of the room. It sounded like it was a small room anyways. but if you want to save money, you could probably score a used one also. ( the used gear option had to rear its head into this ).. but dummy speakers look really loud to people who see sound.
I know nothing about the other drivers you guys were talking about. but it triggered some thoughts to consider.
Xmax maybe high for the 2268 driver and those graphs were really impressive and everything and I WISH I could make those measurements because there are a lot of questions I could answer. (for example, I'd love to see an impedence plot for SRX subs).
those graphs were made using sine waves right?
I was thinking about how amps are capable of delivering some nice impulse power sometimes-- short quick sounds probably wont overheat a 2268 and the excursion will probably be closest to Xmax on a kick. or from the "pluck" on the bass guitar. that Xmax comes in handy for creating punchy music-- some bands hear with their eyes..but they also like to feel the kick. My old sub was an MP418-- I know the kick wasn't really very punchy but a low bass not would get the room vibrating at some frequencies. I could be wrong, but I attribute that at least in part to Xmax. perhaps with more power, I could have made it hit harder.. it only had 500 watts on it.
As Art or someone had pointed out -- you certainly don't want to be at risk of exceeding Xmax. Whether I went with one or two subs, I'd probably get the JBL driver.
Now remember, this thinking is coming from a guy would probably never make a DIY 718. but just thinking about it, you could probably get your tuning and have a longer narrower subwoofer that fit better into the room. There could be some saved space involved. But on the other hand, with a SRX 718, you get that nice heavy grill on the front which can take kicks and bumps. That alone is somethign to consider in bar.
on the other hand, saving money is nice. but then you can make a low-ball offer on used gear and might get lucky. Just think, if you could score a factory sub, wouldn't that be sweet?
I made speaker stands once out of wood. the materials cost was over $200 all said and done. Plywood is expensive. The guy could be an excellent carpenter but its still a pain in the neck to make speaker cabinets.
I'd love to hear the drivers in a DIY though. I'm really curious to hear them actually. I'd like to know if JBL has come up with some "magic" measurements or how much of those dimensions are a tradeoff. It seems the shape of the 718 is to maximize the surface area on the ground.
That said, I know of a place that has them flown on the ceiling.
Need I say more on that?